diff --git a/src/indexer.h b/src/indexer.h
index 6ed84d5b..25757a45 100644
--- a/src/indexer.h
+++ b/src/indexer.h
@@ -63,7 +63,7 @@ struct Id {
   // Needed for google::dense_hash_map.
   explicit operator RawId() const { return id; }
 
-  bool HasValue() const { return id != RawId(-1); }
+  bool HasValueForMaybe_() const { return id != RawId(-1); }
 
   bool operator==(const Id& o) const { return id == o.id; }
   bool operator!=(const Id& o) const { return id != o.id; }
@@ -112,7 +112,7 @@ struct Reference {
   SymbolKind kind;
   Role role;
 
-  bool HasValue() const { return range.HasValue(); }
+  bool HasValueForMaybe_() const { return range.HasValueForMaybe_(); }
   operator SymbolIdx() const { return {id, kind}; }
   std::tuple<Range, Id<void>, SymbolKind, Role> ToTuple() const {
     return std::make_tuple(range, id, kind, role);
diff --git a/src/maybe.h b/src/maybe.h
index eb482e50..60942f1d 100644
--- a/src/maybe.h
+++ b/src/maybe.h
@@ -4,6 +4,8 @@
 
 #include <utility>
 
+// Like optional, but the stored data is responsible for containing the empty
+// state. T should define a function `bool T::HasValueForMaybe_()`.
 template <typename T>
 class Maybe {
   T storage;
@@ -27,7 +29,7 @@ public:
   T& operator*() { return storage; }
 
   bool has_value() const {
-    return storage.HasValue();
+    return storage.HasValueForMaybe_();
   }
   explicit operator bool() const { return has_value(); }
   operator optional<T>() const {
diff --git a/src/position.h b/src/position.h
index b01f696e..8d238b55 100644
--- a/src/position.h
+++ b/src/position.h
@@ -15,7 +15,7 @@ struct Position {
   Position(int16_t line, int16_t column);
   explicit Position(const char* encoded);
 
-  bool HasValue() const { return line >= 0; }
+  bool HasValueForMaybe_() const { return line >= 0; }
   std::string ToString();
   std::string ToPrettyString(const std::string& filename);
 
@@ -39,7 +39,7 @@ struct Range {
   Range(Position start, Position end);
   explicit Range(const char* encoded);
 
-  bool HasValue() const { return start.HasValue(); }
+  bool HasValueForMaybe_() const { return start.HasValueForMaybe_(); }
   bool Contains(int line, int column) const;
   Range RemovePrefix(Position position) const;